Orthopedic casts are typically formed by placing a protective sleeve over a body member and wrapping the protective sleeve with padding to cushion the body member. Once the padding is in place, a roll of flexible, warp-knit fiberglass fabric webbing impregnated with water-activated casting material is wet with water, unrolled and wrapped around the body member. The casting material then sets and hardens forming a cast.
Warp-knit fiberglass is used in casting bandages due to its strength and flexibility. Such fabrics are knit in long lengths and cut into individual casting bandages. Problems arise from use of glass fiber, however, with respect to the tendency of the glass fiber to unravel and fray, particularly on the leading and trailing edges of the elongated fabric.
Initial solutions to the fraying problem proposed in the art include methods involving heat cleaning of the fiberglass to remove starch finish on the fiberglass yarn prior to impregnating the bandage with the water-activated casting material. This method, while providing a tighter fabric having less tendency to fray, adversely affects the ability of the fiberglass to stretch.
Subsequently, it was proposed that a non-heat cleaned fiberglass fabric which has a water-activated resin impregnated casting material compatible with the starch finish on the fiberglass yarn could be used. A two-bar, warp-knit fabric of acceptable stretch character made of non-heat cleaned fiberglass having such a compatible resin was developed and has been successfully marketed under the trademark K-Cast by the Kirschner Medical Corporation of Timonium, Md. These non-heat treated bandages, while preserving the fiberglass stretch characteristics, still have a tendency to unravel and fray.
A further proposed solution to the fraying problem is the use of warp-knit polyester fabric. While such a fabric reduces fraying, it lacks the desirable characteristics of fiberglass.
More recently, U.S. Pat. No. 4,745,912 which is herein incorporated by reference, proposes the addition of a dual fiberglass/thermoplastic fill yarn provided by a back beam to a non-heat treated fiberglass warp yarn to form a fabric which is subjected to heat bonding in order to prevent fraying. This fabric due to its density, however, decreases the flexibility of the fabric.
Therefore, there is a need in the art for a fiberglass warp-knit fabric which does not unravel and fray, but which still retains all the favorable characteristics of a fiberglass fabric casting bandage.